<!DOCTYPE html>
<html lang="en">

<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0">
  <title>Document</title>
  <style>
    #border-btn {
      display: flex;
      align-items: center;
      justify-content: center;
      height: 100vh;
    }

    button {
      border: 0;
      border-radius: 10px;
      background: #2ec4b6;
      /* 文字变大写 */
      text-transform: uppercase;
      color: white;
      font-size: 16px;
      font-weight: bold;
      padding: 15px 30px;
      outline: none;
      position: relative;
      /* 添加动画，对元素的 border-radius 添加 3s 的延迟效果 */
      transition: border-radius 3s;
      -webkit-transition: border-radius 3s;
    }

    button:hover {
      border-bottom-right-radius: 50px;
      border-top-left-radius: 50px;
      border-bottom-left-radius: 10px;
      border-top-right-radius: 10px;
    }
  </style>
</head>

<body>
  <div id="border-btn">
    <button>Hover me</button>
  </div>


</body>

</html>